1. Field of the Invention
The present invention relates to a slave circuit of a LIN bus and a method for operation.
2. Description of the Background Art
A LIN bus (LIN=Local Interconnect Network) is a type of fieldbus. The LIN bus was developed for the communication of intelligent sensors and actuators in motor vehicles. Typical application examples include networking within a door or a seat. A LIN is composed of a LIN master and one or more LIN slaves. The LIN master has knowledge about the time sequence of all data to be transmitted. This data is transmitted by the appropriate LIN slaves when they are requested to do so by the LIN master. The request takes place through the transmission of a header that is characterized by a specific message address. In this context, the header is transmitted by the master. The slave then places the data bytes on the bus after the header.
A LIN transceiver provides the physical bus coupling. A level below 40% of the supply voltage is interpreted by the receiver as a logic zero. Receivers interpret levels greater than 60% of the supply voltage as logic one. In terms of circuitry, a LIN cluster corresponds to an open-collector circuit. A pull-up resistor ensures that the bus level is close to the supply voltage (high level) when the transmitting transistors of all LIN nodes are off. The bus level is pulled close to ground (low level) as soon as a transmitting transistor is on. Accordingly, the low state is called the dominant level, and the high state is called the recessive level.
The LIN specification has two network node states: sleep mode and normal mode. The transition between the two modes is initiated either by an explicit command from the LIN master or via a wake-up signal frame from the LIN master or one of the LIN slaves.